，并集- cluster point
- cluster point compactness
- cluster prime
- cluster sample
- cluster sampling
- cluster set
- cluster value
- cluster value theorem
- C-matrix
- CM field
- CMS (= Chinese Mathematical Society)
- CM-type
- cn
- c-net
- CN-group
- cntracted Bianchi identities
- coabsolute
- coabsolute compactum
- coabsolute space
- coadjoint
- coadjoint functor
- coadjoint orbit
- coadjoint representation
- coadjunction
- coalescence